Additional recommended knowledge

Chemically, dipipanone belongs to the class of opiates called the 3-diphenyl heptanones. It closely resembles methadone, the only structural difference being the N,N-dimethyl moiety of methadone being replaced with a piperidine ring. It's usage is now officially discouraged because of the abuse risk. The combination with cyclizine lends a very strong rush if the drug is injected. During the late 1970s to early 1980s in the UK, a whole spate of deaths were blamed on this preparation.
As supplies became unavailable, opiate users would mix crushed methadone tablets with crushed Valoid (a cyclizine containing antihistamine) tablets in an attempt to replecate the affect of dipipanone.

See P. A. J. Janssen, Synthetic Analgesics. Part 1. Diphenylpropylamines, Pergamon Press, NY. for details on the synthesis of methadone and its cogeners before 1960. The general procedure for synthesis is illustrated by nucleophillic attack of diphenylacetonitrile on 2-chloro--1-dimethylaminoethane. The resulting aminonitrile is then converted to the ethyl ketone with ethyl magnesium bromide by way of the kitimine which is hydrolized by cold aqueous acid (Casey & Parfitt, Opioid Analgesics, Plenum Press, NY, london).